The invention relates to means for the use of an anticoagulant in connection with autotransfusion of blood. Customarily, an intraoperative autotransfusion system includes a suction wand for aspirating blood from an open wound site, a blood reservoir for collecting the aspirated blood and a flexible conduit for conducting the blood from the wand to the reservoir. To prevent clotting of the aspirated blood, it is often desirable to add an effective anticoagulant to the blood as, or promptly after, it is aspirated. The desirable proportion of anticoagulant to blood is generally fixed within a specific range. Anticoagulant can be added through a side port of the wand into a blood flow passageway or lumen where it mixes with the blood as it flows through the wand during aspiration. Commonly, a tube connects the site of anticoagulant entry at the wand with a source of anticoagulant positioned at a particular, generally remote and fixed height.
As discussed in the copending application of Clive Miles and Gary Schneiderman entitled "Autotransfusion System With Anticoagulant Delivery System", the delivery of anticoagulant to the blood depends in part on the height at which the wand is operated (i.e., the height of the wound site) relative to the height location of the anticoagulant source. This is because the driving force for anticoagulant delivery from the anticoagulant source to the blood flowing through the wand generally depends upon several factors, including the hydrostatic head of anticoagulant associated with the height difference between the anticoagulant source and the site of anticoagulant entry into the wand. A change in the operating elevation of the wand relative to the anticoagulant source may therefore affect the driving force for anticoagulant, thus altering the proportion of anticoagulant to blood so that the desired range of said proportion may be exceeded.
The anticoagulant system described herein is particularly designed to compensate for the effects of changes in the aspirating wand elevation relative to the anticoagulant source. The system utilized in the present disclosure represents an improvement over the structure disclosed in the aforementioned copending application of Clive Miles and Gary Schneiderman.